1. Field of the Invention
The present invention relates to a scanning optical system using a laser diode array, and an image recording apparatus including the scanning optical system.
2. Description of the Related Art
In an image recording apparatus including a scanning optical system, such as a laser printer, or a copier machine, high speeds of image formation and high image densities are desirable. It is known that this can be achieved by using a scanning optical system including a plurality of laser beams to scan the surface of a photoconductor medium at the same time, and, laser diode arrays are widely used in the scanning optical system to emit the laser beams.
When using the laser diode arrays, in order that the scanning optical system forms scanning lines on the surface of the photoconductor medium having constant intervals, the laser diodes in a laser diode array, or a laser driving unit in which the laser diode array is installed, are arranged to be inclined relative to the main scan direction.
However, the laser diodes are usually inclined in different ways, and furthermore in different laser driving units, and even in the same laser diode array, the intervals between two laser diodes are not constant. Consequently, the laser diodes in a scanning optical system have different intervals in the main scan direction.
In the related art, in order to reduce the interval fluctuation in each laser driving unit, when mounting the laser driving unit to an image recording apparatus, it is required to adjust the light emission timings of the laser diodes of the laser diode array according to the interval differences of the laser diodes. Further, when the laser driving unit is changed in repairing an image recording apparatus of a user, additional interval fluctuation of the laser diodes may occur, and this causes degradation of the image quality.